Ultrasoft, sensitive fiber-like sensor by assembly of bacterial cellulose (BC) nanofibrils and BC molecules for biocompatible strain sensing

The development of implantable bioelectronics is driven by emerging applications including continuous health monitoring and human-machine interfacing. The mechanical mismatch between implanted bioelectronics and tissues not only compromises device accuracy, but also causes interference with tissues undesirably. To address this issue, it is necessary to develop ultrasoft and biocompatible fiber strain sensor with proper stretchability and sensitivity. Here, we fabricate a bacterial cellulose-based sensing fiber which possesses the stretchability and elastic modulus (~ 102 kPa) close to those of soft tissues. In addition, such fiber has high sensitivity to tiny tensile force/strain (8.8 × 10⁻³ N/2.5%) and low cell cytotoxicity. These excellent properties make the bacterial cellulose (BC)-based sensing fiber an excellent candidate of implantable bioelectric devices for monitoring subtle motions of organs. We demonstrate this by applying it for continuous monitoring of human pulse and bullfrog heartbeats. The (BC/oxBC)@PANI (ox = oxidized and PANI = polyaniline) fibers can further be woven into an array sensor and serve more complex sensing functions, such as multipoint force perception and shape recognition as demonstrated.